1. Field of the Invention
The present invention relates generally to a magnetic memory device and a method of manufacturing the same, and more particularly to a magnetic random access memory (MRAM) and a method of manufacturing the same.
2. Description of the Related Art In a conventional cross-point type MRAM, for example, an MTJ (Magnetic Tunnel Junction) element is, in many cases, provided at a cross point between a bit line and a word line, and the word line is formed such that a metal such as Cu (copper) is buried in a trench in an insulation layer.
After a wiring layer such as a word line is formed in the trench by means of a damascene method, however, it is necessary to subject the metal to a wet etching process or heating treatment, thereby to enhance insulation properties (see, e.g. U.S. Pat. No. 6,261,953). In the step of wet etching, surface roughness occurs on the metal. In the heating treatment, too, surface roughness occurs on the metal since grain boundaries grow in the metal. If such surface roughness occurs on the metal and the surface of the word line becomes uneven, the cross-sectional shape of the MTJ element that is provided on the word line (WL) tends to be distorted in accordance with the uneven surface of the word line.